Cardinals starting pitcher Chris Carpenter suffered a lower back injury during a recent bullpen session, and this setback has caused his rehab regimen to be put on hold.

This apparently happened a few days ago, but Cardinals general manager John Mozeliak didn't reveal it until Thursday, at which point he said Carpenter's status has improved.

"We don't think it's as serious as we first thought," Mozeliak said, via the Associated Press. "It's slowing things down. Hopefully we can continue to work at it. As you can tell, we've got to be patient here."

As Mozeliak has stressed ever since word got out that Carpenter had a shot to return to the team this season, any contribution that he can provide would amount to gravy. The team entered the season expecting to be without Carpenter, and thus far they have the best record in the majors.

As things currently stand, there's no timetable, and Carpenter is still awaiting a firm diagnosis on his back issue from team doctors in St. Louis.

Carpenter is 144-94 with a 3.76 ERA and 1.28 WHIP in his career. He won the 2005 NL Cy Young and has two World Series rings. Due to injuries, though, he only made seven combined starts in 2003, 2007, 2008 and 2012. And, obviously, he's yet to appear in a game in 2013.